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| United States Patent |
6,004,633
|
|
Reinecke
, et al.
|
December 21, 1999
|
Method of producing integrated electrodes in plastic dies, plastic dies
containing integrated electrodes and application of the same
Abstract
Patterned dies made of non-conductive resins may be equipped with
integrated electrodes in different manners. It is proved to be difficult
to produce high-quality electrodes especially in microstructured dies. A
patterned plastic die arranged on a carrier plate is filled with a
solution of a metal compound. This solution is irradiated through the
carrier plate from the back side of the carrier plate using laser light,
ultraviolet light or X-rays. The metal compound is transformed in the
immediate vicinity of the base of the structure and a metal layer is
deposited on the base of the structure forming the electrodes. The method
is suitable for a base of the structure forming a coherent or a
non-coherent area. Plastic dies containing integrated electrodes are used
for electroless or electrophoretic deposition of materials and for
electroplating, in all cases starting from the integrated electrodes, and
for analytical methods.
| Inventors:
|
Reinecke; Holger (Rulzheim, DE);
Noker; Friedolin Franz (Karlsruhe, DE)
|
| Assignee:
|
Microparts Gesellschaft (Dortmund, DE)
|
| Appl. No.:
|
725178 |
| Filed:
|
October 3, 1996 |
Foreign Application Priority Data
| Oct 04, 1995[DE] | 195 36 901 |
| Current U.S. Class: |
427/581; 427/123; 427/404 |
| Intern'l Class: |
C23C 018/14 |
| Field of Search: |
427/581,123,404
204/486
205/184
|
References Cited
U.S. Patent Documents
| 5405656 | Apr., 1995 | Ishikawa et al. | 427/581.
|
| Foreign Patent Documents |
| 4125863 | Feb., 1993 | DE.
| |
| 41 25 863 | Feb., 1993 | DE.
| |
| 60-218580 | Sep., 1987 | JP.
| |
| WO 94/06952 | Mar., 1994 | WO.
| |
Other References
Patent Abstracts of Japan, vol. 9, No. 32, (C-265) [1755], Feb. 9, 1985,
JP-59-177385, Oct. 8, 1984.
|
Primary Examiner: Mayekar; Kishor
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
What is claimed as new and desired to be secured by Letters: Patent of the
United States is:
1. A method of producing integrated electrodes in patterned plastic dies
made of non-conductive resins, comprising the steps of:
producing a patterned plastic die arranged on an upper side of a carrier
plate, said carrier plate being transparent to electromagnetic radiation
and said patterned plastic die having cavities, said cavities each having
a bottom,
filling the cavities of the patterned plastic die with a solution of a
metal compound,
irradiating the solution of the metal compound with electromagnetic
radiation from an underside of the carrier plate, said underside being the
back side of the carrier plate, via the carrier plate, to deposit a metal
layer on the bottoms of the cavities to form the integrated electrodes,
and
removing the solution of the metal compound from the cavities of the
patterned plastic die.
2. The method according to claim 1, wherein the patterned plastic die and
the carrier plate are made of a uniform resin.
3. The method according to claim 1, wherein the patterned plastic die
consists of a first resin and the carrier plate consists of a second
resin.
4. The method according to claim 1, further comprising the step of
machining the back side of the carrier plate to a thickness and surface
smoothness suited for irradiation.
5. The method according to claim 1, comprising the step of filling the
cavities of the patterned plastic die with the solution of one of an
inorganic salt, an organic salt and a metal complex.
6. The method according to claim 1 wherein the step of irradiating the
solution of the metal compound uses one of laser light, ultraviolet light
and X-rays.
7. The method according to claim 1 comprising the step of partially
irradiating the solution of the metal compound with regionally different
intensity.
8. The method according to claim 1 comprising the step of irradiating the
solution of the metal compound through a mask which is arranged on the
back side of the carrier plate and which is locally impermeable to the
applied electromagnetic radiation.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing integrated
electrodes in plastic dies containing cavities, to plastic dies with
integrated electrodes and to applications of the same.
2. Description of the Related Art DE 35 37 483 describes a method for the
formation of a multitude of plate-shaped metallic microstructured bodies
by molding a microstructured tool with a non-conductive molding compound.
Thus a negative mold of the microstructured tool is filled up with metal
by electrodeposition. Then the negative mold is removed. A removable
conductive material is applied to the front surface of the tool. During
molding this conductive material is transferred to the regions of the
molding compound which are in contact with the front surface of the tool.
In a variation of this method, the non-conductive molding compound which
fills up the spaces in the microstructured tool may be fixed by a layer of
a conductive molding compound. The conductive molding compound contacts
and covers the whole front surface of the tool.
DE 40 10 669 describes a method for producing negative molds of
plate-shaped microstructured bodies. The base structure of the patterned
negative mold forms a coherent area which is covered with a layer of
conductive material. This negative mold may be filled with a metal by
electroplating. A layer of a thermoplastic resin which is covered with a
thin film of a conductive material is used for producing the negative
mold. A mold insert is pressed into the heat softened layer of the
thermoplastic resin via the thin conductive film. After cooling the
thermoplastic resin, the negative mold is separated from the mold insert.
During the stamping process the coherent film of conductive material is
split at the front surface of the mold insert corresponding to the pattern
of the microstructure. The regions of the conductive film on the front
surface of the mold insert stick to the front surface. During stamping the
other regions of the film are pushed to the base of the structure of the
mold insert by the thermoplastic resin flowing into the cavities of the
mold insert.
Pieces of the film may remain as tinsel on the side walls of the structure.
If necessary, the tinsel is removed from the negative mold by a laborious
cleaning procedure before the negative mold is electroplated with metal.
After demolding, the regions of the front surface of the mold insert form
the base of the structure of the negative mold. This base is covered with
a coherent conductive film which is contactable at its edge.
The tinsel on the side walls and on the front surface of the negative mold
comes from the conductive film which is imperfectly split during the
stamping process. Some tinsel touches on the conductive layer at the base
of the negative mold structure. This results in partially conductive side
walls of the structure and the directed deposition of metal in the
negative mold is disturbed. Defects, cavities and thicker regions of the
metal layer are thus created in the metallic microstructured body molded
by electroplating.
The conductive film preferably consists of gold, copper, silver and alloys
thereof or of carbon. A film like that on the coherent area of the base of
the structure is suitable as an electrode for the electrodeposition of
other metals, e.g., copper or nickel. This film is less suitable for the
electroless deposition of these metals.
SUMMARY OF THE INVENTION
An object of the invention is to provide a method of producing integrated
electrodes in patterned plastics dies more economically and to produce
high-quality electrodes even in microstructured dies made of
non-conductive resins.
This object is achieved, according to the present invention, by a method
including the steps of producing a structured plastic die on a carrier
plate which is transparent to electromagnetic radiation, filling the
structure of the plastic die with a solution of a metal compound,
irradiating the solution of the metal compound with electromagnetic
radiation from the back side of the carrier plate via the carrier plate so
that the electrodes are formed on the base of the structure, and removing
the solution of the metal compound from the structure of the patterned
plastic die.
The patterned plastic die is produced by injection molding, reaction
molding, thermoforming or some other method using a structured tool. After
solidification of the resin within the tool the plastic die is separated
from the tool. The resin structure complementary to the structure of the
tool is located on a carrier plate having a certain thickness.
For producing the patterned plastic die on a carrier plate either a uniform
resin is used or for the carrier plate a resin is used which is different
from the resin used for the patterned layer. In the latter case, inter
alia, the transparency of the resin for the carrier plate may be matched
to the wavelength of the electromagnetic radiation applied. The carrier
plate may be machined down from its back side to a thickness and a surface
condition suitable for irradiation.
Suitable thermoplastic resins include, e.g., poly(methyl methacrylate),
poly(oxymethylene), acrylonitril-butadiene-styrene and polyamide.
The term "solution of a metal compound" means a solution in the narrow
sense, a suspension or a colloidal solution. The metal compound is a
compound in the narrow sense, a metal complex or a metal itself. The
dissolved metal compound may be an inorganic salt (e.g., silver nitrate,
gold sulfite), an organic metal compound (e.g., palladium acetate, silver
tosylate) or a metal complex (e.g., an amino complex like diamine silver
complex or tetramine copper complex). The solution may contain several
metals at the same time.
The solution of the metal compound filled into the cavities of the plastic
die is irradiated from the back side through the carrier plate using laser
light, ultraviolet light or X-rays. The radiation may enter the whole back
side of the carrier plate with the same intensity or may enter the back
side after passing a patterned mask which lies loosely on the back side of
the carrier plate or which is fixed to the carrier plate as, e.g., a
sputtered mask.
After irradiating, the solution of the metal compound is removed from the
patterned plastic die (e.g., by rinsing).
During irradiation of the solution through the carrier plate the metal
compound is transformed only in the immediate vicinity of the base of the
structure, by which the metal is deposited on the base of the structure in
a layer thus forming the electrodes. Owing to its lower transparency for
the electromagnetic radiation applied, this layer prevents the dissolved
metal compound from further transformation as well as the deposition of
metal on the side walls of the structure even during continuous
irradiation.
The wavelength of the electromagnetic radiation applied and the duration of
the irradiation are matched to the resin employed for the carrier plate,
to the thickness of the carrier plate and to the nature of the metal
compound. If desired, the electrode may be reprecipitated, coated or
etched and may be matched to certain requirements of the following process
steps.
The base of the structure of the patterned plastic die may be coherent or
not coherent. In the first case the integrated electrode is coherent and
is therefore contactable at one point. In the second case the integrated
electrodes are not coherent and are therefore contactable at several
points.
A structure having a coherent electrode is suitable for electroless and
electrophoretic deposition of a material as well as for electroplating,
starting from the conductive electrode. A structure having non-coherent
electrodes is suitable almost only for electroless deposition of a
material, starting from the electrodes. Preferably, palladium solutions
are used for the formation of electrodes necessary for the electroless
deposition of metal. Nickel, copper, gold and other materials can be
electrolessly deposited on a palladium electrode.
The electrodes on the base of the structure of the plastic die may consist
of one layer or of several layers. The formation of two-layer electrodes
starts from a patterned plastic die with integrated electrodes produced
according to the method described above. The solution or suspension of a
metal, a metal compound, a resin, a sintered material or a ceramic
material is filled into the cavities of a patterned plastic die with
integrated electrodes. A layer of the dissolved or suspended material is
deposited as second layer upon the integrated electrodes. The material may
be deposited with or without an electric current. As soon as the second
layer has reached its desired thickness the solution or suspension of the
material is removed from the patterned plastic die.
This process is repeated several times for the formation of multi-layer
electrodes consisting of different materials.
The method according to the invention is preferably applied to
microstructured plastic dies consisting of non-conductive resins.
Patterned plastic dies made of non-conductive resins containing integrated
electrodes arranged on the base of the structure may be used for various
purposes, e.g., for deposition of metal with or without electric current
for producing a metallic patterned body, electrophoretic deposition of
ceramics, metals, metal alloys, resins or sintered materials for producing
a patterned body consisting of one of the deposited materials, an
analytical system, preferably macro-analytical systems. In the first two
cases the deposition of the material starts on the integrated electrodes.
The structure of the body formed by deposited material is complementary to
the structure of the plastic die.
The body formed by material deposited in the patterned plastic die
containing integrated electrodes may consist of a uniform material or the
body may consist of different materials arranged in layers one above the
other.
When the patterned plastic die with integrated electrodes has been used for
the deposition of material, the plastic die is separated mechanically from
the formed structured body or the plastic die is (as dead mold) dissolved
out of the structured body. The integrated electrodes are positioned upon
the front surface of the structured body and are, if necessary, removed
from the front surface, e.g., by selective etching.
The method according to the invention has the following advantages: The
integrated electrodes are positioned only on the base area of the
structure of the plastic die. No tinsel sticks to the side walls of the
structure. The deposition of material with or without electric current in
the patterned plastic die starts from the electrodes only. The deposition
process proceeds undisturbed; no defects, no thicker regions of the
deposited material and no cavities are created during this process within
the structured body.
Preferably, such metals are used for the integrated electrodes which are
especially suitable for the electroless deposition of material in the
plastic die. The embossed unfinished part used for producing the patterned
plastic die is employed without any pretreatment. The resin used for the
carrier plate may be matched to the irradiation process, the resin used
for the patterned layer may be matched to the deposition process. The
electrodes arranged on the base of the structure are formed separately
from the production of the plastic die. After removal of the solution of
the metal compound out of the patterned plastic die, this die may be used
directly for the deposition process. The plastic die may be mechanically
separated from the structured body formed by deposition of material.
Optionally this die may be used repeatedly. The plastic die containing
integrated electrodes is suitable for electroless or electrophoretic
deposition and for electrodeposition of material within the plastic die as
well as for analytical methods.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and many of the attendant
advantages thereof will be readily obtained as the same becomes better
understood by reference to the following detailed description when
considered in connection with the accompanying drawings, wherein:
FIG. 1 shows a plastic die having a grid-like structure in plan view and in
longitudinal view; and
FIG. 2 shows a patterned plastic die having an insular structure in plan
view and in longitudinal view.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows a plastic die having a grid-like structure in plan view and in
longitudinal view. The grid (3) protrudes above the carrier plate (1)
having a smooth back side (2). The grid forms a coherent area (4). Within
and outside this area are insular cavities (5). The base of the structure
has an insular pattern and forms a non-coherent area (6). Integrated
electrodes (7) are arranged on the base of the structure.
FIG. 2 shows a patterned plastic die having an insular structure in plan
view and in longitudinal view. Islands (8) protrude above the carrier
plate (1) having a smooth back side (2). Cavities (5) are arranged between
the islands. The base of the structure is grid-like and forms a coherent
area. An integrated electrode (7) is arranged on the base of the
structure.
EXAMPLE 1
Manufacturing of Microstructured Filter Disks.
The filter disks to be made of nickel have a hexagonal honeycomb pattern
with following dimensions:
Outside diameter of the disks: 3 mm
Diameter of the inside circle of the honeycombs: 80 .mu.m
Width of the honeycomb walls: 8 .mu.m
Height of the honeycomb walls: 270 to 280 .mu.m
The plastic die has a complementary structure but a height of the pattern
of 300 .mu.m.
The microstructured tool made of nickel the structure of which corresponds
to the structure of the filter disks contains structures for a total of
105 filter disks on an area of 60 mm.times.22 mm. Using this tool 105
plastic dies made of poly(methyl methacrylate) are produced, the
microstructure of which in the patterned layer is complementary to the
microstructure of the tool. The microstructure 300 .mu.m high is arranged
on a carrier plate 1.5 mm thick made of poly(methyl methacrylate).
The cavities of the patterned plastic die are coherent within each filter
disk. However, between the cavities of two filter disks no connection
exists. So the base of the structure of all 105 filter disks together is
not coherent.
First, the cavities of the patterned plastic die are filled free of bubbles
with an aqueous solution containing 0.3 mol silver acetate per liter. The
plastic die is irradiated for 2 minutes by means of a mercury-vapor lamp
(100 W power) arranged in a distance of 1.5 cm from the back side of the
carrier plate. During this irradiation electrodes are formed as dense
silver layers on the base of the structure of the plastic die. The silver
acetate solution is sucked out of the plastic die and the plastic die is
rinsed with high-purity water.
Then the cavities of this patterned plastic die are filled free of bubbles
with an aqueous solution containing 2.0 mmol palladium chloride per liter.
After 15 minutes at room temperature the silver layer on the base of the
structure is replaced by a palladium layer. The palladium chloride
solution is sucked out of the plastic die and the plastic die is rinsed
with high-purity water. The non-coherent palladium layer forms electrodes
on the base of the structure of the plastic die.
The plastic die is immersed in a solution of 50 g nickel chloride per liter
for the electroless deposition of nickel in the cavities of the plastic
die. After 21 hours at about 60.degree. C. the cavities of the plastic die
are filled with nickel to a height of 276 .mu.m.
The plastic die filled with nickel is removed from the nickel bath and is
rinsed with high-purity water. Finally, the plastic die is dissolved in
hot ethyl acetate by which the filter disks are separated from the plastic
die and are present as isolated pieces. So the additional partition of the
filter disks by mechanical reworking of the outside contours is neither
necessary nor permissible due to the narrow dimensional tolerances and the
required low roughness.
EXAMPLE 2
Producing a Heatable Analytical Device.
An analytical device consists of a Y-shaped flow splitter containing
electrodes on the coherent area of the base of the structure. A liquid
passing this structure is heated by means of electrically heated
electrodes.
A plastic die made of polysulfon (10 mm wide, 20 mm long, 3 mm thick) is
produced by injection molding. The Y-shaped channel is 1 mm wide and 1 mm
deep. A solution containing 0.1 mol gold sulfate per liter is filled into
the cavities of the structure. The plastic die is irradiated from its back
side using an ultraviolet lamp (1 kW power) which is arranged at a
distance of 40 cm from the plastic die. A convex quartz lens is located
between the ultraviolet lamp and the plastic die. After 45 minutes
irradiation time a dense gold layer is formed on the base of the
structure. The solution of gold sulfite is removed from the plastic die
and the die is rinsed with high-purity water.
Then the plastic die is immersed in a solution from which a copper-nickel
alloy is deposited electrolytically. The current density is 1 A/dm.sup.2.
A layer 1.2 .mu.m thick is formed on the base of the structure within 10
minutes at 65.degree. C. The plastic die is taken out of the bath and is
rinsed and dried. A plastic cover plate is applied over the die. Lead-in
wires are fixed to the electrodes. A liquid in the Y-shaped flow splitter
is heated by resistance heating.
This device is used within an analytical system for heating up a liquid in
which system a chemical reaction is investigated photometrically.
Obviously, numerous modifications and variations of the present invention
are possible in light of the above teachings. It is therefore to be
understood that the invention may be practiced otherwise than as
specifically described herein.
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